Cerebral veins show wide variation, and unexpected veins occasionally limit surgical procedures for clipping of cerebral aneurysms. This study was undertaken to assess the utility of three-dimensional CT angiography (3D-CTA) in the evaluation of venous anatomy before surgical clipping of cerebral aneurysms. 3D-CTA was performed in 19 patients before pterional craniotomy. The venous anatomy visualized by use of 3D-CTA was compared retrospectively with intraoperative findings. 3D-CTA clearly depicted the superficial sylvian veins (SSVs) in 17 of 19 cases. In three of these 17 cases, 3D-CTA failed to reveal the additional connecting veins from SSVs to the midportion of the sphenoid wing. 3D-CTA also depicted bridging veins from: 1) the basal vein of Rosenthal to the sphenoparietal sinus (SPS) (three cases); 2) a junction of the anterior cerebral vein and the deep middle cerebral vein to the SPS (two cases); 3) the anterior cerebral vein into the cavernous sinus (one case); and 4) the deep middle cerebral vein to the cavernous sinus in one case. Surgical findings corresponded well with the angiographic findings. 3D-CTA depicted bridging veins from the frontal base into the SPS in two cases; retraction of the frontal lobe was severely limited in these cases. 3D-CTA also exhibited anatomic variation of deep cerebral veins, which suggests the utility of 3D-CTA in evaluating the risks carried by sacrifice of some bridging veins. In two patients, aneurysmal dissection was restricted because of adhering veins. 3D-CTA depicted these cerebral veins to be lying in contact with the aneurysm. In one case, the contiguous vein was hidden behind a large middle cerebral artery aneurysm; 3D-CTA was helpful for visualization of this vein. 3D-CTA can clearly depict the venous anatomy of the brain and is useful for surgical planning of a pterional or temporopolar approach for cerebral aneurysms.